/*

Copyright (c) 2006-2021, Arvid Norberg

Copyright (c) 2016-2017, 2020, Alden Torres

Copyright (c) 2016-2017, Andrei Kurushin

Copyright (c) 2016, Falcosc

Copyright (c) 2016, Steven Siloti

Copyright (c) 2017, Pavel Pimenov

Copyright (c) 2021, Dmtry Soloviev

All rights reserved.

Redistribution and use in source and binary forms, with or without

modification, are permitted provided that the following conditions

are met:

 * Redistributions of source code must retain the above copyright

  notice, this list of conditions and the following disclaimer.

 * Redistributions in binary form must reproduce the above copyright

  notice, this list of conditions and the following disclaimer in

  the documentation and/or other materials provided with the distribution.

 * Neither the name of the author nor the names of its

  contributors may be used to endorse or promote products derived

  from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE

LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

POSSIBILITY OF SUCH DAMAGE.

*/

#include "libtorrent/config.hpp"

#include <functional>

#include <cstdlib>

#include <cstdio> // for snprintf

#include <cinttypes> // for PRId64 et.al.

#include "libtorrent/web_peer_connection.hpp"

#include "libtorrent/session.hpp"

#include "libtorrent/entry.hpp"

#include "libtorrent/bencode.hpp"

#include "libtorrent/alert_types.hpp"

#include "libtorrent/aux_/invariant_check.hpp"

#include "libtorrent/io.hpp"

#include "libtorrent/parse_url.hpp"

#include "libtorrent/peer_info.hpp"

#include "libtorrent/aux_/session_interface.hpp"

#include "libtorrent/aux_/alert_manager.hpp" // for alert_manager

#include "libtorrent/aux_/escape_string.hpp" // for escape_path

#include "libtorrent/hex.hpp" // for is_hex

#include "libtorrent/random.hpp"

#include "libtorrent/torrent.hpp"

#include "libtorrent/http_parser.hpp"

namespace libtorrent {

constexpr int request_size_overhead = 5000;

std::string escape_file_path(file_storage const& storage, file_index_t index);

web_peer_connection::web_peer_connection(peer_connection_args& pack

  , web_seed_t& web)

  : web_connection_base(pack, web)

  , m_url(web.url)

  , m_web(&web)

  , m_received_body(0)

  , m_chunk_pos(0)

  , m_partial_chunk_header(0)

  , m_num_responses(0)

{

  INVARIANT_CHECK;

  if (!m_settings.get_bool(settings_pack::report_web_seed_downloads))

    ignore_stats(true);

  std::shared_ptr<torrent> tor = pack.tor.lock();

  TORRENT_ASSERT(tor);

  // if the web server is known not to support keep-alive. request 4MiB

  // but we want to have at least piece size to prevent block based requests

  int const min_size = std::max((web.supports_keepalive ? 1 : 4) * 1024 * 1024,

    tor->torrent_file().piece_length());

  // we prefer downloading large chunks from web seeds,

  // but still want to be able to split requests

  int const preferred_size = std::max(min_size, m_settings.get_int(settings_pack::urlseed_max_request_bytes));

  prefer_contiguous_blocks(preferred_size / tor->block_size());

  std::shared_ptr<torrent> t = associated_torrent().lock();

  bool const single_file_request = t->torrent_file().num_files() == 1;

  if (!single_file_request)

  {

    // handle incorrect .torrent files which are multi-file

    // but have web seeds not ending with a slash

    ensure_trailing_slash(m_path);

    ensure_trailing_slash(m_url);

  }

  else

  {

    // handle .torrent files that don't include the filename in the url

    if (m_path.empty()) m_path += '/';

    if (m_path[m_path.size() - 1] == '/')

    {

      m_path += escape_string(t->torrent_file().name());

    }

    if (!m_url.empty() && m_url[m_url.size() - 1] == '/')

    {

      m_url += escape_file_path(t->torrent_file().orig_files(), file_index_t(0));

    }

  }

  // we want large blocks as well, so

  // we can request more bytes at once

  // this setting will merge adjacent requests

  // into single larger ones

  request_large_blocks(true);

#ifndef TORRENT_DISABLE_LOGGING

  peer_log(peer_log_alert::info, "URL", "web_peer_connection %s", m_url.c_str());

#endif

}

std::string escape_file_path(file_storage const& storage, file_index_t index)

{

  std::string new_path { storage.file_path(index) };

#ifdef TORRENT_WINDOWS

  convert_path_to_posix(new_path);

#endif

  return escape_path(new_path);

}

void web_peer_connection::on_connected()

{

  peer_id pid;

  aux::random_bytes(pid);

  set_pid(pid);

  if (m_web->have_files.empty())

  {

    incoming_have_all();

  }

  else if (m_web->have_files.none_set())

  {

    incoming_have_none();

    m_web->interesting = false;

#ifndef TORRENT_DISABLE_LOGGING

    peer_log(peer_log_alert::info, "WEB-SEED", "have no files, not interesting. %s", m_url.c_str());

#endif

  }

  else

  {

    std::shared_ptr<torrent> t = associated_torrent().lock();

    // only advertise pieces that are contained within the files we have as

    // indicated by m_web->have_files AND padfiles!

    // it's important to include pieces that may overlap many files, as long

    // as we have all those files, so instead of starting with a clear bitfield

    // and setting the pieces corresponding to files we have, we do it the

    // other way around. Start with assuming we have all files, and clear

    // pieces overlapping with files we *don't* have.

    typed_bitfield<piece_index_t> have;

    file_storage const& fs = t->torrent_file().files();

    have.resize(fs.num_pieces(), true);

    for (auto const i : fs.file_range())

    {

      // if we have the file, no need to do anything

      if (m_web->have_files.get_bit(i) || fs.pad_file_at(i)) continue;

      auto const range = aux::file_piece_range_inclusive(fs, i);

      for (piece_index_t k = std::get<0>(range); k < std::get<1>(range); ++k)

        have.clear_bit(k);

    }

    t->set_seed(peer_info_struct(), false);

    if (have.none_set())

    {

      incoming_have_none();

      m_web->interesting = false;

#ifndef TORRENT_DISABLE_LOGGING

      peer_log(peer_log_alert::info, "WEB-SEED", "have no pieces, not interesting. %s", m_url.c_str());

#endif

    }

    else

    {

      incoming_bitfield(have);

    }

  }

  // TODO: 3 this should be an optional<piece_index_t>, piece index -1 should

  // not be allowed

  if (m_web->restart_request.piece != piece_index_t(-1))

  {

    // increase the chances of requesting the block

    // we have partial data for already, to finish it

    incoming_suggest(m_web->restart_request.piece);

  }

  web_connection_base::on_connected();

}

void web_peer_connection::disconnect(error_code const& ec

  , operation_t op, disconnect_severity_t const error)

{

  if (is_disconnecting()) return;

  if (op == operation_t::sock_write && ec == boost::system::errc::broken_pipe)

  {

#ifndef TORRENT_DISABLE_LOGGING

    // a write operation failed with broken-pipe. This typically happens

    // with HTTP 1.0 servers that close their incoming channel of the TCP

    // stream whenever they're done reading one full request. Instead of

    // us bailing out and failing the entire request just because our

    // write-end was closed, ignore it and keep reading until the read-end

    // also is closed.

    peer_log(peer_log_alert::info, "WRITE_DIRECTION", "CLOSED");

#endif

    // prevent the peer from trying to send anything more

    m_send_buffer.clear();

    // when the web server closed our write-end of the socket (i.e. its

    // read-end), if it's an HTTP 1.0 server. we will stop sending more

    // requests. We'll close the connection once we receive the last bytes,

    // and our read end is closed as well.

    incoming_choke();

    return;

  }

  if (op == operation_t::connect && m_web && !m_web->endpoints.empty())

  {

    // we failed to connect to this IP. remove it so that the next attempt

    // uses the next IP in the list.

    m_web->endpoints.erase(m_web->endpoints.begin());

  }

  if (ec == errors::uninteresting_upload_peer && m_web)

  {

    // if this is an "ephemeral" web seed, it means it was added by receiving

    // an HTTP redirect. If we disconnect because we're not interested in any

    // of its pieces, mark it as uninteresting, to avoid reconnecting to it

    // repeatedly

    if (m_web->ephemeral) m_web->interesting = false;

    // if the web seed is not ephemeral, but we're still not interested. That

    // implies that all files either have failed with 404 or with a

    // redirection to a different web server.

    m_web->retry = std::max(m_web->retry, aux::time_now32()

      + seconds32(m_settings.get_int(settings_pack::urlseed_wait_retry)));

    TORRENT_ASSERT(m_web->retry > aux::time_now32());

  }

  std::shared_ptr<torrent> t = associated_torrent().lock();

  if (!m_requests.empty() && !m_file_requests.empty()

    && !m_piece.empty() && m_web)

  {

#ifndef TORRENT_DISABLE_LOGGING

    if (should_log(peer_log_alert::info))

    {

      peer_log(peer_log_alert::info, "SAVE_RESTART_DATA"

        , "data: %d req: %d off: %d"

        , int(m_piece.size()), int(m_requests.front().piece)

        , m_requests.front().start);

    }

#endif

    m_web->restart_request = m_requests.front();

    if (!m_web->restart_piece.empty())

    {

      // we're about to replace a different restart piece

      // buffer. So it was wasted download

      if (t) t->add_redundant_bytes(int(m_web->restart_piece.size())

        , waste_reason::piece_closing);

    }

    m_web->restart_piece = std::move(m_piece);

    // we have to do this to not count this data as redundant. The

    // upper layer will call downloading_piece_progress and assume

    // it's all wasted download. Since we're saving it here, it isn't.

    m_requests.clear();

  }

  if (m_web && !m_web->supports_keepalive && error == peer_connection_interface::normal)

  {

    // if the web server doesn't support keepalive and we were

    // disconnected as a graceful EOF, reconnect right away

    if (t) post(get_context()

      , std::bind(&torrent::maybe_connect_web_seeds, t));

  }

  if (error >= failure)

  {

    m_web->retry = std::max(m_web->retry, aux::time_now32()

      + seconds32(m_settings.get_int(settings_pack::urlseed_wait_retry)));

  }

  peer_connection::disconnect(ec, op, error);

  TORRENT_ASSERT(m_web->resolving == false);

  m_web->peer_info.connection = nullptr;

}

piece_block_progress web_peer_connection::downloading_piece_progress() const

{

  if (m_requests.empty()) return {};

  std::shared_ptr<torrent> t = associated_torrent().lock();

  TORRENT_ASSERT(t);

  piece_block_progress ret;

  ret.piece_index = m_requests.front().piece;

  ret.bytes_downloaded = int(m_piece.size());

  // this is used to make sure that the block_index stays within

  // bounds. If the entire piece is downloaded, the block_index

  // would otherwise point to one past the end

  int correction = m_piece.empty() ? 0 : -1;

  ret.block_index = (m_requests.front().start + int(m_piece.size()) + correction) / t->block_size();

  TORRENT_ASSERT(ret.block_index < int(piece_block::invalid.block_index));

  TORRENT_ASSERT(ret.piece_index < piece_block::invalid.piece_index);

  ret.full_block_bytes = t->block_size();

  piece_index_t const last_piece = t->torrent_file().last_piece();

  if (ret.piece_index == last_piece && ret.block_index

    == t->torrent_file().piece_size(last_piece) / t->block_size())

  {

    ret.full_block_bytes = t->torrent_file().piece_size(last_piece) % t->block_size();

  }

  return ret;

}

void web_peer_connection::write_request(peer_request const& r)

{

  INVARIANT_CHECK;

  std::shared_ptr<torrent> t = associated_torrent().lock();

  TORRENT_ASSERT(t);

  TORRENT_ASSERT(t->valid_metadata());

  torrent_info const& info = t->torrent_file();

  peer_request req = r;

  std::string request;

  request.reserve(400);

  int size = r.length;

  const int block_size = t->block_size();

  const int piece_size = t->torrent_file().piece_length();

  peer_request pr{};

  while (size > 0)

  {

    int request_offset = r.start + r.length - size;

    pr.start = request_offset % piece_size;

    pr.length = std::min(std::min(block_size, size), piece_size - pr.start);

    pr.piece = piece_index_t(static_cast<int>(r.piece) + request_offset / piece_size);

    TORRENT_ASSERT(validate_piece_request(pr));

    m_requests.push_back(pr);

    if (m_web->restart_request == m_requests.front())

    {

      TORRENT_ASSERT(int(m_piece.size()) == m_received_in_piece);

      TORRENT_ASSERT(m_piece.empty());

      m_piece = std::move(m_web->restart_piece);

      peer_request const& front = m_requests.front();

      TORRENT_ASSERT(front.length > int(m_piece.size()));

#ifndef TORRENT_DISABLE_LOGGING

      peer_log(peer_log_alert::info, "RESTART_DATA",

        "data: %d req: (%d, %d) size: %d"

          , int(m_piece.size()), static_cast<int>(front.piece), front.start

          , front.start + front.length - 1);

#else

      TORRENT_UNUSED(front);

#endif

      req.start += int(m_piece.size());

      req.length -= int(m_piece.size());

      // just to keep the accounting straight for the upper layer.

      // it doesn't know we just re-wrote the request

      incoming_piece_fragment(int(m_piece.size()));

      m_web->restart_request.piece = piece_index_t(-1);

      TORRENT_ASSERT(int(m_piece.size()) == m_received_in_piece);

    }

#if 0

      std::cerr << this << " REQ: p: " << pr.piece << " " << pr.start << std::endl;

#endif

    size -= pr.length;

  }

#ifndef TORRENT_DISABLE_LOGGING

  peer_log(peer_log_alert::outgoing_message, "REQUESTING", "(piece: %d start: %d) - (piece: %d end: %d)"

    , static_cast<int>(r.piece), r.start

    , static_cast<int>(pr.piece), pr.start + pr.length);

#endif

  bool const single_file_request = t->torrent_file().num_files() == 1;

  int const proxy_type = m_settings.get_int(settings_pack::proxy_type);

  bool const using_proxy = (proxy_type == settings_pack::http

    || proxy_type == settings_pack::http_pw) && !m_ssl;

  // the number of pad files that have been "requested". In case we _only_

  // request padfiles, we can't rely on handling them in the on_receive()

  // callback (because we won't receive anything), instead we have to post a

  // pretend read callback where we can deliver the zeroes for the partfile

  int num_pad_files = 0;

  // TODO: 3 do we really need a special case here? wouldn't the multi-file

  // case handle single file torrents correctly too?

  if (single_file_request)

  {

    file_request_t file_req;

    file_req.file_index = file_index_t(0);

    file_req.start = std::int64_t(static_cast<int>(req.piece)) * info.piece_length()

      + req.start;

    file_req.length = req.length;

    request += "GET ";

    // do not encode single file paths, they are

    // assumed to be encoded in the torrent file

    request += using_proxy ? m_url : m_path;

    request += " HTTP/1.1\r\n";

    add_headers(request, m_settings, using_proxy);

    request += "\r\nRange: bytes=";

    request += to_string(file_req.start).data();

    request += "-";

    request += to_string(file_req.start + file_req.length - 1).data();

    request += "\r\n\r\n";

    m_first_request = false;

    m_file_requests.push_back(file_req);

  }

  else

  {

    std::vector<file_slice> files = info.orig_files().map_block(req.piece, req.start

      , req.length);

    for (auto const &f : files)

    {

      file_request_t file_req;

      file_req.file_index = f.file_index;

      file_req.start = f.offset;

      file_req.length = int(f.size);

      if (info.orig_files().pad_file_at(f.file_index))

      {

        m_file_requests.push_back(file_req);

        ++num_pad_files;

        continue;

      }

      request += "GET ";

      if (using_proxy)

      {

        // m_url is already a properly escaped URL

        // with the correct slashes. Don't encode it again

        request += m_url;

      }

      auto redirection = m_web->redirects.find(f.file_index);

      if (redirection != m_web->redirects.end())

      {

        auto const& redirect = redirection->second;

        // in case of http proxy "request" already contains m_url with trailing slash, so let's skip dup slash

        bool const trailing_slash = using_proxy && !redirect.empty() && redirect[0] == '/';

        request.append(redirect, trailing_slash, std::string::npos);

      }

      else

      {

        if (!using_proxy)

        {

          // m_path is already a properly escaped URL

          // with the correct slashes. Don't encode it again

          request += m_path;

        }

        request += escape_file_path(info.orig_files(), f.file_index);

      }

      request += " HTTP/1.1\r\n";

      add_headers(request, m_settings, using_proxy);

      request += "\r\nRange: bytes=";

      request += to_string(f.offset).data();

      request += "-";

      request += to_string(f.offset + f.size - 1).data();

      request += "\r\n\r\n";

      m_first_request = false;

#if 0

      std::cerr << this << " SEND-REQUEST: f: " << f.file_index

        << " s: " << f.offset

        << " e: " << (f.offset + f.size - 1) << std::endl;

#endif

      // TODO: 3 file_index_t should not allow negative values

      TORRENT_ASSERT(f.file_index >= file_index_t(0));

      m_file_requests.push_back(file_req);

    }

  }

  if (num_pad_files == int(m_file_requests.size()))

  {

    post(get_context(), std::bind(

      &web_peer_connection::on_receive_padfile,

      std::static_pointer_cast<web_peer_connection>(self())));

    return;

  }

#ifndef TORRENT_DISABLE_LOGGING

  peer_log(peer_log_alert::outgoing_message, "REQUEST", "%s", request.c_str());

#endif

  send_buffer(request);

}

namespace {

  std::string get_peer_name(http_parser const& p, std::string const& host)

  {

    std::string const& server_version = p.header("server");

    if (!server_version.empty())

      return server_version;

    return host;

  }

  std::tuple<std::int64_t, std::int64_t> get_range(

    http_parser const& parser, error_code& ec)

  {

    std::int64_t range_start;

    std::int64_t range_end;

    if (parser.status_code() == 206)

    {

      std::tie(range_start, range_end) = parser.content_range();

      if (range_start < 0 || range_end < range_start)

      {

        ec = errors::invalid_range;

        range_start = 0;

        range_end = 0;

      }

      else

      {

        // the http range is inclusive

        range_end++;

      }

    }

    else

    {

      range_start = 0;

      range_end = parser.content_length();

      if (range_end < 0)

      {

        range_end = 0;

        ec = errors::no_content_length;

      }

    }

    return std::make_tuple(range_start, range_end);

  }

}

// --------------------------

// RECEIVE DATA

// --------------------------

bool web_peer_connection::received_invalid_data(piece_index_t const index, bool single_peer)

{

  if (!single_peer) return peer_connection::received_invalid_data(index, single_peer);

  // when a web seed fails a hash check, do the following:

  // 1. if the whole piece only overlaps a single file, mark that file as not

  //    have for this peer

  // 2. if the piece overlaps more than one file, mark the piece as not have

  //    for this peer

  // 3. if it's a single file torrent, just ban it right away

  // this handles the case where web seeds may have some files updated but not other

  std::shared_ptr<torrent> t = associated_torrent().lock();

  file_storage const& fs = t->torrent_file().files();

  // single file torrent

  if (fs.num_files() == 1) return peer_connection::received_invalid_data(index, single_peer);

  std::vector<file_slice> files = fs.map_block(index, 0, fs.piece_size(index));

  if (files.size() == 1)

  {

    // assume the web seed has a different copy of this specific file

    // than what we expect, and pretend not to have it.

    auto const range = file_piece_range_inclusive(fs, files[0].file_index);

    for (piece_index_t i = std::get<0>(range); i != std::get<1>(range); ++i)

      incoming_dont_have(i);

  }

  else

  {

    incoming_dont_have(index);

  }

  peer_connection::received_invalid_data(index, single_peer);

  // if we don't think we have any of the files, allow banning the web seed

  if (num_have_pieces() == 0) return true;

  // don't disconnect, we won't request anything from this file again

  return false;

}

void web_peer_connection::on_receive_padfile()

{

  handle_padfile();

}

void web_peer_connection::handle_error(int const bytes_left)

{

  std::shared_ptr<torrent> t = associated_torrent().lock();

  TORRENT_ASSERT(t);

  // TODO: 2 just make this peer not have the pieces

  // associated with the file we just requested. Only

  // when it doesn't have any of the file do the following

  // pad files will make it complicated

  // temporarily unavailable, retry later

  t->retry_web_seed(this, m_parser.header_duration("retry-after"));

  if (t->alerts().should_post<url_seed_alert>())

  {

    std::string const error_msg = to_string(m_parser.status_code()).data()

      + (" " + m_parser.message());

    t->alerts().emplace_alert<url_seed_alert>(t->get_handle(), m_url

      , error_msg);

  }

  received_bytes(0, bytes_left);

  disconnect(error_code(m_parser.status_code(), http_category()), operation_t::bittorrent, failure);

}

void web_peer_connection::disable(error_code const& ec)

{

  // we should not try this server again.

  m_web->disabled = true;

  disconnect(ec, operation_t::bittorrent, peer_error);

  if (m_web->ephemeral)

  {

    std::shared_ptr<torrent> t = associated_torrent().lock();

    TORRENT_ASSERT(t);

    t->remove_web_seed_conn(this);

  }

  m_web = nullptr;

  TORRENT_ASSERT(is_disconnecting());

}

void web_peer_connection::handle_redirect(int const bytes_left)

{

  // this means we got a redirection request

  // look for the location header

  std::string location = m_parser.header("location");

  received_bytes(0, bytes_left);

  std::shared_ptr<torrent> t = associated_torrent().lock();

  TORRENT_ASSERT(t);

  if (location.empty())

  {

    disable(errors::missing_location);

    return;

  }

  bool const single_file_request = !m_path.empty()

    && m_path[m_path.size() - 1] != '/';

  // when SSRF mitigation is enabled, a web seed on the internet (is_global())

  // is not allowed to redirect to a server on the local network, so we set

  // the no_local_ips flag

  auto const web_seed_flags = torrent::ephemeral

    | ((m_settings.get_bool(settings_pack::ssrf_mitigation) && aux::is_global(remote().address()))

      ? torrent::no_local_ips : web_seed_flag_t{});

  // add the redirected url and remove the current one

  if (!single_file_request)

  {

    TORRENT_ASSERT(!m_file_requests.empty());

    file_index_t const file_index = m_file_requests.front().file_index;

    location = resolve_redirect_location(m_url, location);

#ifndef TORRENT_DISABLE_LOGGING

    peer_log(peer_log_alert::info, "LOCATION", "%s", location.c_str());

#endif

    // TODO: 3 this could be made more efficient for the case when we use an

    // HTTP proxy. Then we wouldn't need to add new web seeds to the torrent,

    // we could just make the redirect table contain full URLs.

    std::string redirect_base;

    std::string redirect_path;

    error_code ec;

    std::tie(redirect_base, redirect_path) = split_url(location, ec);

    if (ec)

    {

      // we should not try this server again.

      disconnect(errors::missing_location, operation_t::bittorrent, failure);

      return;

    }

    // add_web_seed won't add duplicates. If we have already added an entry

    // with this URL, we'll get back the existing entry

    // "ephemeral" flag should be set to avoid "web_seed_t" saving in resume data.

    // E.g. original "web_seed_t" request url points to "http://example1.com/file1" and

    // web server responses with redirect location "http://example2.com/subpath/file2".

    // "handle_redirect" process this location to create new "web_seed_t"

    // with base url=="http://example2.com/" and redirects[0]=="/subpath/file2").

    // If we try to load resume with such "web_seed_t" then "web_peer_connection" will send

    // request with wrong path "http://example2.com/file1" (cause "redirects" map is not serialized in resume)

    web_seed_t* web = t->add_web_seed(redirect_base, web_seed_entry::url_seed

      , m_external_auth, m_extra_headers, web_seed_flags);

    web->have_files.resize(t->torrent_file().num_files(), false);

    // the new web seed we're adding only has this file for now

    // we may add more files later

    web->redirects[file_index] = redirect_path;

    if (web->have_files.get_bit(file_index) == false)

    {

      web->have_files.set_bit(file_index);

      if (web->peer_info.connection != nullptr)

      {

        auto* pc = static_cast<peer_connection*>(web->peer_info.connection);

        // we just learned that this host has this file, and we're currently

        // connected to it. Make it advertise that it has this file to the

        // bittorrent engine

        file_storage const& fs = t->torrent_file().files();

        auto const range = aux::file_piece_range_inclusive(fs, file_index);

        for (piece_index_t i = std::get<0>(range); i < std::get<1>(range); ++i)

          pc->incoming_have(i);

      }

      // we just learned about another file this web server has, make sure

      // it's marked interesting to enable connecting to it

      web->interesting = true;

    }

    // we don't have this file on this server. Don't ask for it again

    m_web->have_files.resize(t->torrent_file().num_files(), true);

    if (m_web->have_files[file_index])

    {

      m_web->have_files.clear_bit(file_index);

#ifndef TORRENT_DISABLE_LOGGING

      peer_log(peer_log_alert::info, "MISSING_FILE", "redirection | file: %d"

        , static_cast<int>(file_index));

#endif

    }

    disconnect(errors::redirecting, operation_t::bittorrent, normal);

  }

  else

  {

    location = resolve_redirect_location(m_url, location);

#ifndef TORRENT_DISABLE_LOGGING

    peer_log(peer_log_alert::info, "LOCATION", "%s", location.c_str());

#endif

    t->add_web_seed(location, web_seed_entry::url_seed, m_external_auth

      , m_extra_headers, web_seed_flags);

    // this web seed doesn't have any files. Don't try to request from it

    // again this session

    m_web->have_files.resize(t->torrent_file().num_files(), false);

    disconnect(errors::redirecting, operation_t::bittorrent, normal);

    m_web = nullptr;

    TORRENT_ASSERT(is_disconnecting());

  }

}

void web_peer_connection::on_receive(error_code const& error

  , std::size_t bytes_transferred)

{

  INVARIANT_CHECK;

  if (error)

  {

    received_bytes(0, int(bytes_transferred));

#ifndef TORRENT_DISABLE_LOGGING

    if (should_log(peer_log_alert::info))

    {

      peer_log(peer_log_alert::info, "ERROR"

        , "web_peer_connection error: %s", error.message().c_str());

    }

#endif

    return;

  }

  std::shared_ptr<torrent> t = associated_torrent().lock();

  TORRENT_ASSERT(t);

  // in case the first file on this series of requests is a padfile

  // we need to handle it right now

  span<char const> recv_buffer = m_recv_buffer.get();

  handle_padfile();

  if (associated_torrent().expired()) return;

  for (;;)

  {

    int payload;

    int protocol;

    bool header_finished = m_parser.header_finished();

    if (!header_finished)

    {

      bool failed = false;

      std::tie(payload, protocol) = m_parser.incoming(recv_buffer, failed);

      received_bytes(0, protocol);

      TORRENT_ASSERT(int(recv_buffer.size()) >= protocol);

      if (failed)

      {

        received_bytes(0, int(recv_buffer.size()));

#ifndef TORRENT_DISABLE_LOGGING

        if (should_log(peer_log_alert::info))

        {

          peer_log(peer_log_alert::info, "RECEIVE_BYTES"

            , "%*s", int(recv_buffer.size()), recv_buffer.data());

        }

#endif

        disconnect(errors::http_parse_error, operation_t::bittorrent, peer_error);

        return;

      }

      TORRENT_ASSERT(recv_buffer.empty() || recv_buffer[0] == 'H');

      TORRENT_ASSERT(int(recv_buffer.size()) <= m_recv_buffer.packet_size());

      // this means the entire status line hasn't been received yet

      if (m_parser.status_code() == -1)

      {

        TORRENT_ASSERT(payload == 0);

        break;

      }

      if (!m_parser.header_finished())

      {

        TORRENT_ASSERT(payload == 0);

        break;

      }

      m_body_start = m_parser.body_start();

      m_received_body = 0;

    }

    // we just completed reading the header

    if (!header_finished)

    {

      ++m_num_responses;

      if (m_parser.connection_close())

      {

        incoming_choke();

        if (m_num_responses == 1)

          m_web->supports_keepalive = false;

      }

#ifndef TORRENT_DISABLE_LOGGING

      if (should_log(peer_log_alert::info))

      {

        peer_log(peer_log_alert::info, "STATUS"

          , "%d %s", m_parser.status_code(), m_parser.message().c_str());

        auto const& headers = m_parser.headers();

        for (auto const &i : headers)

          peer_log(peer_log_alert::info, "STATUS", "   %s: %s", i.first.c_str(), i.second.c_str());

      }

#endif

      // if the status code is not one of the accepted ones, abort

      if (!is_ok_status(m_parser.status_code()))

      {

        if (!m_file_requests.empty())

        {

          file_request_t const& file_req = m_file_requests.front();

          m_web->have_files.resize(t->torrent_file().num_files(), true);

          m_web->have_files.clear_bit(file_req.file_index);

#ifndef TORRENT_DISABLE_LOGGING

          peer_log(peer_log_alert::info, "MISSING_FILE", "http-code: %d | file: %d"

            , m_parser.status_code(), static_cast<int>(file_req.file_index));

#endif

        }

        handle_error(int(recv_buffer.size()));

        return;

      }

      if (is_redirect(m_parser.status_code()))

      {

        handle_redirect(int(recv_buffer.size()));

        return;

      }

      m_server_string = get_peer_name(m_parser, m_host);

      recv_buffer = recv_buffer.subspan(m_body_start);

      m_body_start = m_parser.body_start();

      m_received_body = 0;

    }

    // we only received the header, no data

    if (recv_buffer.empty()) break;

    // ===================================

    // ======= RESPONSE BYTE RANGE =======

    // ===================================

    // despite the HTTP range being inclusive, range_start and range_end are

    // exclusive to fit better into C++. i.e. range_end points one byte past

    // the end of the payload

    std::int64_t range_start;

    std::int64_t range_end;

    error_code ec;

    std::tie(range_start, range_end) = get_range(m_parser, ec);

    if (ec)

    {

      received_bytes(0, int(recv_buffer.size()));

      disable(ec);

      return;

    }

    TORRENT_ASSERT(!m_file_requests.empty());